一、什么是session？
Session由服务器创建，并为每一次会话分配一个Session对象。同一个浏览器发起的多次请求，同属于一次会话（Session）。首次使用到Session时，服务器会自动创建Session，并创建Cookie来存储Session ID发送回客户端。Session ID用于唯一标识一个会话，确保在同一个会话中请求被正确地处理。
一台服务器对应多个客户端，服务器如何知道谁是谁 ---》 通过cookies和session进行匹配的
每个测览器访可同一个站点的不同方法的时候都会携带一个cookie，名字叫JSESSICNID给服务器，服务器将JSESSIONID的值作为sesion的id进行存诸，通过这两个进行匹配，找到对应的客户端
先看实现效果是如何滴？
输入验证码，前端发送请求到后端，后端接收，存入session，并且后端校验验证码是否正确，将结果返回前端，并设置了验证码的有效时间为1min，1分钟过后过期
话不多说，来实现这个功能！
二、代码
前端：cookie，后端：session
思路：
前端页面一加载调用验证码的生成（created），输入验证码，点击登录按钮，发送到后端进行处理和判断【首先从session取出来验证码，然后进行判断，返回前端】
验证码用session存，调用验证码的工具类，生成图片验证码，然后将验证码存入session，在设置有效的时间为60s
前端相关的代码：
<el-button @click="doLogin">登录</el-button>
//验证码，点击验证码可以改变
<p style="margin-left: 100px">验证码：<input type="text" v-model="code">
< class="changeCodeImg" :src="codeUrl" alt="" @click="changeCode">
</p>javascript"> data(){
return{
code:"",
codeUrl:"http://localhost:9091/api/code/createCode",
}
},
created(){
this.changeCode()
},
methods:{
//点击图片改变
changeCode(){
//看你后端接口的路径哦，如果写完了想看路径对不对，可以通过直接访问路径得到验证码图片
this.codeUrl="http://localhost:9091/api/code/createCode
},
}
重头戏的是后端的啦，看看后端怎么实现🤔
后端相关代码：
点击登录按钮时判断验证码是否正确，返回结果给前端
java">//controller
//点击登录按钮判断验证码是否正确
@RequestMapping("/login")
public ResponseDto login(@RequestBody LoginVo vo, HttpSession session){
System.out.println(session.getAttribute("code"));
//先判断验证码是否正确，正确在进行账号密码的判断
if (vo.getCode().equals(session.getAttribute("code"))){
//登录验证码如果成功要做的事情
*****
}else if (session.getAttribute("code") == null){
//ResponseDto是我写的返回消息的工具类
return new ResponseDto(-1,"验证码过期",null);
}else {
return new ResponseDto(2,"验证码错误",null);
}
}java">import com.cykj.util.ImageCodeUtils;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import java.io.IOException;
@RestController
@RequestMapping("/code")
public class CodeController {
@RequestMapping("/createCode")
public void createCode(HttpServletResponse response, HttpSession session){
//生成验证码图片的工具类
ImageCodeUtils imageCodeUtils = new ImageCodeUtils();
//将验证码存入session中
session.setAttribute("code",imageCodeUtils.getCode());
//设置有效时间，单位为秒
session.setMaxInactiveInterval(60);
try {
//写回去
imageCodeUtils.write(response.getOutputStream());
} catch (IOException e) {
throw new RuntimeException(e);
}
}
}接下来就是工具类
消息返回工具类
java">public class ResponseDto {
private int code;
private String msg;
private Object data;
public int getCode() {
return this.code;
}
public void setCode(int code) {
this.code = code;
}
public String getMsg() {
return this.msg;
}
public void setMsg(String msg) {
this.msg = msg;
}
public Object getData() {
return this.data;
}
public void setData(Object data) {
this.data = data;
}
public ResponseDto(int code, String msg, Object data) {
this.code = code;
this.msg = msg;
this.data = data;
}
public String toString() {
return "ResponseDto{code=" + this.code + ", msg='" + this.msg + '\'' + ", data=" + this.data + '}';
}
}生成验证码工具类
java">import javax.imageio.ImageIO;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.io.OutputStream;
import java.util.Random;
/**
* @description TODO
* @date 2023/12/21 0:38
*/
public class ImageCodeUtils {
/**
* 图片的宽度
*/
private int width = 160;
/**
* 图片的高度
*/
private int height = 40;
/**
* 验证码字符个数
*/
private int codeCount = 4;
/**
* 验证码干扰线数
*/
private int lineCount = 20;
/**
* 验证码
*/
private String code = null;
private BufferedImage buffImg = null;
Random random = new Random();
public ImageCodeUtils() {
createImage();
}
public ImageCodeUtils(int width, int height) {
this.width = width;
this.height = height;
createImage();
}
public ImageCodeUtils(int width, int height, int codeCount) {
this.width = width;
this.height = height;
this.codeCount = codeCount;
createImage();
}
public ImageCodeUtils(int width, int height, int codeCount, int lineCount) {
this.width = width;
this.height = height;
this.codeCount = codeCount;
this.lineCount = lineCount;
createImage();
}
/**
* 生成图片
*/
private void createImage() {
// 字体的宽度
int fontWidth = width / codeCount;
// 字体的高度
int fontHeight = height - 5;
int codeY = height - 8;
// 图像buffer
buffImg = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
Graphics g = buffImg.getGraphics();
// 设置背景色
g.setColor(getRandColor(200, 250));
g.fillRect(0, 0, width, height);
// 设置字体
//Font font1 = getFont(fontHeight);
Font font = new Font("Fixedsys", Font.BOLD, fontHeight);
g.setFont(font);
// 设置干扰线
for (int i = 0; i < lineCount; i++) {
int xs = random.nextInt(width);
int ys = random.nextInt(height);
int xe = xs + random.nextInt(width);
int ye = ys + random.nextInt(height);
g.setColor(getRandColor(1, 255));
g.drawLine(xs, ys, xe, ye);
}
// 添加噪点
float yawpRate = 0.01f;
int area = (int) (yawpRate * width * height);
for (int i = 0; i < area; i++) {
int x = random.nextInt(width);
int y = random.nextInt(height);
buffImg.setRGB(x, y, random.nextInt(255));
}
// 得到随机字符
String str1 = randomStr(codeCount);
this.code = str1;
for (int i = 0; i < codeCount; i++) {
String strRand = str1.substring(i, i + 1);
g.setColor(getRandColor(1, 255));
// a为要画出来的东西，x和y表示要画的东西最左侧字符的基线位于此图形上下文坐标系的 (x, y) 位置处
g.drawString(strRand, i*fontWidth+3, codeY);
}
}
/**
* 得到随机字符串
* @param n
* @return
*/
private String randomStr(int n) {
String str1 = "ABCDEFGHJKMNOPQRSTUVWXYZabcdefghjkmnopqrstuvwxyz1234567890";
String str2 = "";
int len = str1.length() - 1;
double r;
for (int i = 0; i < n; i++) {
r = (Math.random()) * len;
str2 = str2 + str1.charAt((int) r);
}
return str2;
}
/**
* 得到随机颜色
* @param fc
* @param bc
* @return
*/
private Color getRandColor(int fc, int bc) {
if (fc > 255){
fc = 255;
}
if (bc > 255){
bc = 255;
}
int r = fc + random.nextInt(bc - fc);
int g = fc + random.nextInt(bc - fc);
int b = fc + random.nextInt(bc - fc);
return new Color(r, g, b);
}
/**
* 产生随机字体
*/
private Font getFont(int size) {
Random random = new Random();
Font[] font = new Font[5];
font[0] = new Font("Ravie", Font.PLAIN, size);
font[1] = new Font("Antique Olive Compact", Font.PLAIN, size);
font[2] = new Font("Fixedsys", Font.PLAIN, size);
font[3] = new Font("Wide Latin", Font.PLAIN, size);
font[4] = new Font("Gill Sans Ultra Bold", Font.PLAIN, size);
return font[random.nextInt(5)];
}
/**
* 扭曲方法
* @param g
* @param w1
* @param h1
* @param color
*/
private void shear(Graphics g, int w1, int h1, Color color) {
shearX(g, w1, h1, color);
shearY(g, w1, h1, color);
}
private void shearX(Graphics g, int w1, int h1, Color color) {
int period = random.nextInt(2);
boolean borderGap = true;
int frames = 1;
int phase = random.nextInt(2);
for (int i = 0; i < h1; i++) {
double d = (double) (period >> 1)
* Math.sin((double) i / (double) period
+ (6.2831853071795862D * (double) phase)
/ (double) frames);
g.copyArea(0, i, w1, 1, (int) d, 0);
if (borderGap) {
g.setColor(color);
g.drawLine((int) d, i, 0, i);
g.drawLine((int) d + w1, i, w1, i);
}
}
}
private void shearY(Graphics g, int w1, int h1, Color color) {
int period = random.nextInt(40) + 10;
boolean borderGap = true;
int frames = 20;
int phase = 7;
for (int i = 0; i < w1; i++) {
double d = (double) (period >> 1)
* Math.sin((double) i / (double) period
+ (6.2831853071795862D * (double) phase)
/ (double) frames);
g.copyArea(i, 0, 1, h1, 0, (int) d);
if (borderGap) {
g.setColor(color);
g.drawLine(i, (int) d, i, 0);
g.drawLine(i, (int) d + h1, i, h1);
}
}
}
public void write(OutputStream sos) throws IOException {
ImageIO.write(buffImg, "png", sos);
sos.close();
}
public BufferedImage getBuffImg() {
return buffImg;
}
public String getCode() {
return code.toLowerCase();
}
}
